(a) Field of the Invention
The present invention is related to a tap pressure balance valve, and more particularly to one that maintains normal operation of the tap by having disposed a coil spring and a cut-off washer, or seal, in a through hole of a secondary case at where in relation to an water outlet from a deck of a primary case for the coil spring to push against the cut-off washer to maintain watertightness between the through hole and the water outlet of the primary case thus to prevent seepage from the interface where the primary and the secondary cases are incorporated to each other.
(b) Description of the Prior Art
A mixer valve is usually provided inside a tap so to mix the hot and the cold water before being delivered through a sprout for use. The construction of a mixer valve to a tap of the prior art to mix hot water and cold water tends to focus on the design of mixing without safety measures to cope with abnormal conditions including interrupted supply of water. Therefore, when the supply either of the hot water or the cold water is interrupted, the sprout remains delivery the water to cause sudden supply of hot or cold water only. Sudden cold water supply particularly in the wintertime would expose the user to catch cold; and sudden hot water, to be scalded. To correct this problem, an improvement was introduced by providing a pressure balance valve to automatically stop water delivery in case of sudden interruption of hot or cold water for safety concerns.
The pressure balance valve of the prior art is essentially comprised of having a rubber diaphragm inserted into the space inside a combined case, and a balance valve inserted through a through hole disposed at the center of the diaphragm. In normal supply of cold and hot water, the diaphragm stays at its position in the case while the valve is away from its status to close up both inlets of hot and cold water. When either hot or cold water supply is suddenly interrupted, the changed water pressure causes the diaphragm to be deformed and displaced, leading further to the valve to the end of the water is not interrupted to contact its water inlet and to indicate watertight status. Since the other end of the water is already interrupted, the supply of both hot and cold water is stopped to prevent a sudden supply of cold or hot water only, thus to prevent the user from catching cold or getting scalded.
However, in the prior art, the installation of the diaphragm and the valve is achieved by having their respective cases combined to each other. The possible seepage at the interface between both cases must be taken into consideration. To achieve watertight results, usually a cut-off washer is provided to the interface to present seepage of water from the interface of combination.
Both cases must compress against the cut-off washer for the cut-off washer to achieve the watertight results, i.e., close coordination from the interface of the combined cases must be provided. Any error in the manufacturing process of the interface between the combined cases would fail to provide good watertight results, leading to possible seepage from the interface between the combined cases that may significantly affect the normal operation of the tap as a whole.
Furthermore, a shallow slot may be provided on the case for the insertion of the cut-off; however, insufficient depth of the slot fails to effectively secure the water. As a result, the water is vulnerable to leaking or deflection in the course of the combination of both cases to compromise the assembly quality and function. During the assembly process, greater compression force is required for the cases to secure the cut-off washer for the expected watertight results. Accordingly, how to secure ideal watertight results for the pressure balance valve of the tap becomes the primary target of the R&D efforts for the present invention.